border-1px($color)
   position: relative
   &:after
     position: absolute
     left: 0
     bottom: 0
     width: 100%
     border-top: 1px solid $color
     content: ''

bg-image($url)
    background-image: url($url + '@2x.png')
    @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3)
      background-image: url($url + '@3X.png')